Effect of Construction Material Quality on Structural Stability of Low-Cost Housing in Osun State

The quality of construction materials used in low-cost housing schemes significantly determines the long-term structural stability of the built units, yet procurement standards in this housing category are often compromised by budget constraints. This study evaluates the effect of construction material quality on the structural stability of low-cost residential buildings across three housing estate developments in Osun State within the South West geopolitical zone. Samples of reinforcement bars, cement, and sandcrete blocks were collected from all three sites and subjected to tensile strength, compressive strength, and water absorption tests in accredited laboratories. Structural stability was assessed through visual inspection, crack mapping, and plumb-line measurements of vertical wall deviation. Results reveal that reinforcement bars from two of the three sites failed to meet the minimum yield strength of 250 N/mm2 required by NIS 117, with average values of 201 N/mm2 and 218 N/mm2 respectively. Cement samples from one site exhibited a setting time outside the permitted range, suggesting potential hydration irregularity. Crack densities on walls in the housing estates built with substandard materials were 2.8 times higher than on estates where certified materials were used. The study identifies weak procurement oversight and absence of materials testing at delivery as the root causes of observed quality gaps. Recommendations include mandatory on-site acceptance testing of all structural materials, training of site supervisors, and a centralised materials certification database for public housing projects. Keywords: construction materials, structural stability, low-cost housing, Osun State, material quality.